1. Field of the Invention
The present invention relates to a chucking device and a chucking method.
2. Description of Related Art
In some chucking devices that vacuum-suck a wafer, suction grooves are formed immediately below the wafer. For example, Japanese Unexamined Patent Application Publication No. 2007-250601 discloses a suction pad having suction grooves that are concentrically formed. The suction grooves are evacuated to thereby vacuum-suck a wafer. However, when the wafer has a large warpage, the vacuum leaks from an end of the wafer. As a result, the degree of vacuum cannot be increased, which makes it difficult to vacuum-suck the wafer.
Japanese Unexamined Patent Application Publication No. H11-243135 discloses a vacuum suction pad that vacuum-sucks a wafer. In the vacuum suction pad disclosed in Japanese Unexamined Patent Application Publication No. H11-243135, the vacuum suction is performed in a state where a silicon wafer is placed on a disk-shaped member formed of porous ceramics. In other words, the wafer is secured by vacuum suction through the porous ceramics.
In the vacuum suction pad disclosed in Japanese Unexamined Patent Application Publication No. H11-243135, when the wafer contacts the porous ceramics, microscopic crushing is liable to occur in the porous ceramics, resulting in generation of dust. In the porous ceramics, it is difficult to clean and eliminate foreign matters accumulated in fine recesses. Besides, it is hard to dry cleaning liquid or rinse agent entering into the porous ceramics. Furthermore, since a separate component for preventing a leakage from an end surface or a bottom surface is used, it is necessary to bond the separate component to the porous ceramics with an adhesive. However, the use of an adhesive makes it difficult to perform acid cleaning. Thus, when porous ceramics are used, it is difficult to improve detergent properties.
The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a chucking device having low dusting characteristics and high detergent properties and capable of vacuum-sucking even a substrate having a large warpage, and a chucking method using the same.